Mechanical pipe end seal/alignment device

ABSTRACT

A multi-purpose pipe end seal/alignment device is provided for sealing pipe ends against internal or external pressure while protecting the pipe end preparation from damage to facilitate a permanent pipe joining process at a remote location in an adverse environment.

BACKGROUND OF THE INVENTION

The methods commonly used to cap a pipe end for testing, evacuation,displacing, pulling or submerging a number of end-joined pipes; i.e., apipeline, include a weld cap, a weld and blind flange assembly, ascraper trap type closure device, or in some cases an expandable plug,modified as required for the particular pipeline installationapplication. With the exception of the expandable plug, which isprimarily for line test and evacuation applications, all of theabove-described cap systems require pipeline quality alignment, welding,cutting and rebeveling of the pipe end for line extensions or tie-ins.Accordingly, these prior art systems are both cost and labor intensive.In addition, pipe sizes and lengths are becoming increasingly large,installation areas are more remote and difficult, and material, delaypenalties, and other associated cost factors are becoming increasinglygreater, particularly in the marine activity areas. There is asubstantial need in the art for an improved, time sensitive and moreflexible system of securing combinations of pipe end seals, pipe endprotections, and assisting pipe end alignments for joining.

SUMMARY OF THE INVENTION

The mechanical pipe end seal/alignment device of this invention providesthe flexibility for testing, evacuation, displacing, pulling and/orsubmerging a number of joined pipes, as well as facilitating the pipeend aligning end joint for a tie-in to extend previously installedpipeline segments.

More particularly, the present invention provides a mechanical pipe endseal comprising, in combination, an edge-tapered pipe end cap providedwith an elastomer ring seal engaging and protecting the end periphery ofthe pipe; an edge-tapered pipe slip-on ring, or series of lugs, arrangedfor connection to the pipe outer periphery by encirclement welds; and aninside tapered-hinged closure device arranged to engage the taperededges of the end cap and slip-on ring which thereby positions the ringbetween the pipe and the seal-retained closure cap when the ends of thehinged closure device are drawn together and become tightened, therebysecurely and uniformly compresses the elastomer seal against the pipeend. The end seal system also is provided with an additional means ofpreserving internal pressure as well as maintaining a water-tightintegrity upon submergence for a long-distance tow transport.

Further, the present invention provides an external type of mechanicalpipeline tie-in assembly comprising, in combination, two draw assembliesadapted to grip the slip-on ring means disposed on the outer peripheryof the proximate ends of separate pipes; pipe cradles configured toprovide multi-planar control so as to permit drawing of the pipe endsinto center alignments; studs or cylinder actuators engageable with thedraw assemblies; and means to pull or push the draw assemblies by thestuds or actuators. The seal-retained closure cap and the inside-beveledencirclement ring will have been previously removed but are capable ofrapid re-installation in an emergency-abandonment procedure.

The invention also provides a method for preserving and protecting, aswell as mechanically sealing, a normally-prepared pipe end such as abeveled weld face so as to permit a hydrostatic or pneumatic test of thesealed pipe without damaging the prepared pipe end. The mechanical endseal coupling may be used repeatedly, and in the event of damage to theelastomer seal, requires only the servicing or simple replacement of theelastomer ring seal within a bolt-mounted seal retainer ring. Asupplementing end seal is also capable of being readily installed forpurposes of maintaining a positive internal pressure, or for maintainingthe water-tight integrity of the pipe internals, should the primary sealmechanism be released.

Accordingly, by the above-described apparatus and method, the presentinvention overcomes the above-noted problems of the prior art, andprovides multi-purpose capabilities and other improvements as will bemore particularly described hereinafter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 discloses a cutaway view of a submersible pipeline pull capfitted with a secondary inflatable-bag type pressure seal.

FIG. 2 discloses the elastomer ring seal in a de-energized mode.

FIG. 3 discloses a metallic bellows insert to the elastomer ring seal.

FIG. 4 depicts an alternate-type end secondary pressure seal which is acompressed sphere.

FIG. 5 depicts a pipe end drawup alignment mode.

DESCRIPTION OF PREFERRED EMBODIMENTS

The mechanical pipe end seal/alignment device, described hereinafter, isa multi-purpose tool for the primary use of sealing pipe ends againstinternal or external pressures while protecting the pipe end preparationfrom damage to facilitate the permanent pipe-joining or tie-in processat a remote location in an adverse environment. The device concept is tosatisfy a plurality of repetitive pipeline installation demands in apositive, rapid, effective and cost-sensitive manner. The plurality ofapplications include pipe internal pressure testing; preventingencroachments of pressure when the pipeline is submerged for transport;facilitating pipe end alignments and gap spacements for tie-ins; andproviding a quick, mechanical means of reacquiring a pipe end seal inthe event of an emergency. It is desirable to provide a removable,reusable and readily field-repairable pipeline mechanical end seal whichpreserves the pipe end bevel or similar preparation and to efficientlyhandle the full range of testing sequences such as passage ofline-gaging pigs, passage of line-fill pigs, venting the pipeline,hydrostatic internal pressure tests, and passage of line displacement ordewatering pigs.

A further application of the present invention includes pipeline pullsegment transfer. When long pipeline assemblies are required to bepulled from an assembly and pretest area to a remote pipeline tie-inpoint such as required in offshore, water-course crossings and swamp ormarsh environments, the mechanical end seal device, such as utilized inthe pipe internal pressure testing above described, is fitted with anexternal pull point swivel eye and an inflatable air bag ormechanically-drawn internal pipe plug or sphere-shaped device to serveas a secondary backup seal and thus assure preservation of the pullsegment watertight integrity or bouyancy specification. The secondaryend seal device may also be utilized in an on-bottom placement sequenceto maintain a positive internal pipe pressure so as to protect the pipefrom ovalling due to excessive bending stresses as well as to preventline fill encroachment of a pipe joining area.

Still another application of the invention pertains to pipeline segmenttie-in and on-bottom placement. Securing or maintaining the alignmentand gap spacing of large-diameter pipe ends of long pipeline sections isa difficult and time-consuming task. The pipeline end sealing device, asdescribed in the above two applications, may be removed to expose theundamaged pipe joining surface such as a weld bevel preparation, and theedge-tapered pipe slip-on ring, or weld-on lugs, or packer-type ring.The pipe slip-on ring assembly may then be utilized on some applicationsto facilitate the center alignment and spacement of the undamaged pipeend with a previously-installed pipeline end which may or may not besimilarly fitted. With the assistance of pipe breakover and aligningjack cradles, the slack pipe end may be drawn up through a pair ofoversize bisected, hinged and bolted, or cylinder actuated, slip-overflanges mounted to encapsulate the edge-tapered pipe slip-on ring.Additional ports would be provided in the slip-over flanges to permitinstallation of additional bolt studs and nuts, or cylinder actuators,to maintain continuous pipe end positioning as the tie-in weld encirclesthe pipe. Upon tie-in completion, the alignment assembly is removed forweld inspection, corrosion protection and on-bottom installation. Theedge-tapered slip-on ring would preferably remain on the tie-in jointsince its outside diameter, in most applications, would not exceed theoutside diameter of pipeline weight coat jacketing. Additionally, insome deepwater applications, the slip-on rings would reinforce andstiffen the tie-in joint against buckling and also serve to limit thepropagation of a pipe collapse failure.

Particularly in the offshore environment, weather deteriorations candevelop rapidly and to a point where a pipeline installation processmust cease and require the pipe end to be resealed and placed on bottomin a temporary emergency-abandonment procedure for protection of theinstallation crew and equipment as well as the uncompleted pipeline.Subsequently, the pipeline end must be relocated and recovered for theresumption of the installation process. The mechanical end-closuresystem of the present invention provides an invaluable equipmentaddition for this type of operation.

Some normal offshore pipeline installation procedures, particularly inplatform approach areas, require temporary on-bottom pipeline placementsfor purposes such as surface equipment reorientation, and/or theinstallation of ancilliary pipeline connection assemblies, and thesubsequent end recovery in order to complete the installation process.The mechanical end-closure system of the present invention also providesa simple, rapid and reliable method of facilitating a temporary pipelineon bottom placement and later recovery.

Having above generally described the invention, the following moreparticularly describes the invention with reference to the accompanyingdrawings. FIG. 1 provides a cutaway view of the pipeline mechanical endseal device arranged for a submersible pipeline transport. An elastomerseal 1 engages the end periphery of the pipeline segment 2 having an endbevel for welding, an external corrosion coat 3, and in most cases, aconcrete weight (or protective) jacket 4. The elastomer ring seal iscontained in an edge-tapered pipe end closure cap 5 which will coverpipe 2 and press seal 1 against the pipe when energized. Aninside-tapered device 6, shown in an energized mode, is adapted to alsoengage the edge-tapered slip-on ring lug assembly 7, or alternatively,slip-on ring (not shown) or a mechanical packer (not shown). Themechanical pipe end seal device may also be equipped with a swivel-typepipe pull eye 8 for use as above described in pulling the pipe to remotelocations. An inflated elastomer bag to serve as a pipe end secondaryseal 9 is disposed internally of the pipe within the vicinity of the endseal. Bag 9 may be fitted with a reinforced bag stiffener 10, orstiffeners, shown at the opposite primary seal end, in this arrangementwhich may be bonded or fused to the elastomer bag at one or both, andwhich is also shown in an arrangement with stiffener serrations 11. Thebag, fitted with one or more serrated stiffeners, are intended toprovide a backup or secondary seal protection against leaks into thepipe by externally-applied pressure, such as could occur during offshoretowing of the pipe end, and also to separately provide a means ofmaintaining a positive internal pressure when needed to resist pipeovalling stresses due to external pipe pressure or to prevent a linefill encroachment of a pipe joining area. Energizing ports 12 areprovided in the edge-tapered closure cap 5 where hydraulic fluid orgrease may be admitted to pressurize the ring seal 1. Ring seal retainerring 13 function in cooperation with the pressurizing fluid to furtherseal the lips of the seal around the beveled end of the pipe to provideseal-keeping capabilities and to permit a rapid field replacement of theelastomer ring seal.

Elastomer ring seal 1, shown in an energized position in FIG. 1, isshown in FIG. 2 in a de-energized position. A reinforced wear surface 20is provided to fit about the beveled end of the pipe and therebyprevents excessive seal wear replacement and the inadvertent piercing ofthe seal by the pipe end. A ring seal bellows metallic insert 21,insertible into the elastomer ring seal for admission of hydraulicfluid, grease or other pressurizing mechanism, is more particularlyshown in FIG. 3. The bellows insert has a curved edge 30 which fits intocorresponding grooves 22 in the ring seal 1.

In FIG. 4 is shown an alternate pipe end secondary seal which may besubstituted for inflated elastomer bag 9 shown in FIG. 1. Sphere 40 iscompressed between undersized blind flanges 41 and 42, pulled togetherby threaded bolt 43 into sealing engagement with pipeline segment 2. Thepipe end drawup alignment depicted in FIG. 5 is illustrative of asurface-type connection of two pipelines aboard a lay barge. Otherrepresentations which are not shown may also include a subsurfaceconnection of two submerged pipelines, an on-bottom connection of twopipelines on the seafloor, or an on-bottom connection of a pipeline to afixed platform riser assembly.

FIG. 5 discloses a pipe end drawup alignment mode for the presentinvention which is shown in a surface-type connection arrangement. Inaccordance with this part of the invention, there is provided asuspended pipeline tensioner 50 of the type utilized offshore forholding a prescribed tensile force on a suspended and submerged pipesegment of a pipeline. The pipeline tensioner 50 generally resides in afixed or lockable position on a lay barge. Conventionally, the weld capon the segment which is to become affixed to the tensioned-submergedpipeline segment must be removed with a cutting device and the end ofthe pipe must be beveled, or otherwise prepared for joining, and thenbrought together with the end of the pipeline for welding or otherjoining process. Due to the lay barge reaction to pitch, heave, yaw androll, it is difficult to accomplish this operation and to bring the endof a long multi-joint segment into the specified alignment tolerancewith a fixed pipe end so that they may be welded or otherwise joinedtogether. However, in accordance with the present invention, there isprovided a mechanical pipeline tie-in assembly which includes draw (orpush) assemblies 51 and 52 of the clamp-on type which are adapted toencapsulate and grip lugs 7, or slip-on rings or mechanical packers asabove described, which are disposed on the outer periphery of theproximate ends of the separate pipelines 2 and 54. Pipe alignmentcradles, one of which is shown (cradle 56), is provided withthree-dimensional adjustment and the suspended pipeline tensioner 50 areadapted to bring the ends of the pipelines together whereupon studs 57,actuated cylinders or other means, are engaged with the draw (or push)assemblies and utilized to space the center-aligned pipe end assembliesso that the pipelines can be welded or joined together. Upon jointinspection and approval for installation, an outer concrete or masticencasement of the tie-in joint 58 may encapsulate the lugs 7, or ringsabove described, so that they need not be removed from the pipe afterthe welding operation. Studs 57 fit into split-ring hinges 53 andsplit-ring fasteners 55. Clamp flanges 51 and 52 are provided withmulti-stud ports for a continuous tie-in process whereby the pipe endscan be brought progressively into spacial alignment by tightening theouter or inner nuts 59 so as to securely fix and maintain the pipe endsat the prescribed relationship throughout the joining procedure.

I claim as my invention:
 1. A method for joining a pipe segment to anoffshore pipeline while maintaining pressure in the pipeline to protectit from buckling stresses arising from external pressure and bending,and to protect the joining environment, comprising:maintaining pressurein the pipeline by sealing it with an expandable insert; joining thepipe segment to the pipeline; and transporting the expandable insertthrough and to the free end of the joined pipe segment by overcoming thesliding friction resistance of the expandable insert by relativelyadjusting the pressure exerted by the expandable insert and the pressureinside the pipeline.
 2. The method of claim 1 wherein the pipeline isfurther pressured to move, or transport, the expandable insert.
 3. Themethod of claim 1 wherein pressure exerted by the expandable insert onthe pipeline is reduced to allow the insert to move.